@book{773,
	author = {Ehrlich, Paul R. and Ehrlich, Anne H., },
	title = {Ecoscience :},
	publisher = {W.H. Freeman, },
	year = {c1977},
	address = {San Francisco, CA :},
	url = {https://www.cicy.mx/sitios/sib/doctoelectronico/783.pdf}
}